Plastic has taken the place of other materials in a variety of industries. In the packaging industry, plastic has replaced glass to minimize breakage, reduce weight, and reduce energy consumed in manufacturing and transport. In other industries, plastic has replaced metal to minimize corrosion, reduce weight, and provide color-in-bulk products.
Heat is used in thermoplastics mixing to melt the thermoplastic resin to produce intermediate powder or pellets for later reshaping into a plastic article, a “first heat history”, or the final shaping step itself, a “second heat history.”
Some functional additives are very sensitive to heat. If the functional additive has a relatively high vapor pressure at temperatures required to melt the thermoplastic resin, either during the first heat history or the second heat history, the functional additive (usually the most expensive per unit mass) will vaporize to reduce or even remove all traces of its addition in the final plastic article.